The men dressed in red turbans and long robes and carrying machine guns and machetes handed out amulets that they said would protect people in the coming fight. They went among the Muslim and Christian residents in the northern Nigerian city of Kano saying they meant no harm; their gripe was solely with the national government for failing to live by the Qur'an.

The next day the hundreds of fighters, who included women and some children, attacked the police headquarters, killing 10 policemen and a divisional commander's wife. The police station was set ablaze, vehicles were burned and prisoners freed.

A six-hour battle followed through parts of the city that left at least 10 others dead, some of them civilians caught in the crossfire. About 25 attackers were killed as the army shelled the mixed Panshekara district. Others were captured.

Binta Zakari narrowly escaped being shot. "I saw them attacking with their children and wives. I don't know what they wanted but I was told they are not happy with the state," she said.

No one in Panshekara is even sure who the attackers were. But religious leaders believe they were members of the self-styled "Nigerian Taliban", a group founded by radical students who believe the country is led by an infidel government.

The Nigerian Taliban first emerged five years ago demanding "full sharia" in the 12 states in the north that introduced Islamic law after the end of military rule in 1999. Attacks on symbols of the federal government followed, particularly the police.

The latest assault sent a new wave of fear through Kano's minority Christian community, which lives with one eye on sharia and inter-religious violence that has caused tens of thousands of deaths in recent years with periodic massacres across the country.

Islamist attacks on the Christian areas of Kano have left hundreds dead at a time. In Plateau state, human rights groups have recorded nearly 60,000 religious killings of Muslims and Christians in the past six years. Tens of thousands more have fled their homes.

Before the assault in Kano, the fundamentalists told residents they were avenging the killing of a popular dissident cleric in the city, Sheikh Jafar Adam, who was shot dead by masked men as he led early morning prayers at his mosque.

Some saw a political motive. The murdered sheikh, who had a large following, had fallen out with Kano's governor, Ibrahim Shekarau, for not implementing sharia law strictly enough and quit the commission overseeing Islamic law in protest.

Sharia came to Kano on a wave of popular support in northern Nigeria among voters who hoped it would curb rampant corruption. The state introduced a form of religious police to enforce dress codes, ban the sale of beer and impose a bar on male-driven motorbike taxis carrying women. Earlier this year the national government won a court ruling disbanding the religious police as illegal, to the fury of more radical Islamists.

Sheikh Adam, a Saudi-educated member of the strict Wahhabi sect, was among those who also accused state governments of watering down sharia law, saying that politicians had hijacked a populist issue to get elected but then neutralised it in a classic Nigerian way: the Kano administration established a series of commissions and councils to oversee sharia, gave them large budgets and co-opted many clerics, who bought new cars and bigger houses.

"People have been let down. Corruption was unchecked," said Dr Bashir Aliyu Umar, the new imam of the assassinated sheikh's mosque. "Some of the religious leaders have been compromised by the creation of institutions that support the implementing of sharia. They have sizeable government budgets and have become like other government agencies. They haven't been free of corruption.

"People see that some governors here used the issue of sharia to stay in power and amass a lot of wealth. They see these governors here use sharia in a very evil way to make sure the finger is not pointed at them."

Mr Shekarau is among several northern governors also accused by Nigeria's anti-corruption commission. He was up for re-election last month. The day before his death, Sheikh Adam delivered a sermon in which he said he would direct his followers how to vote. His large following meant that if, as expected, he threw his weight behind the opposition he could have had a significant impact on the election.

The sheikh was shot before he could deliver his instruction. Mr Shekarau was re-elected two days later.

The Nigerian Taliban has also attacked what it says is a western plot to "Christianise" Islam after Kano's leaders sought to offset the influence of Saudi Arabia and Iran, which are funding hardline Islamist schools that some fear are educating a generation of extremists. The Emir of Kano is negotiating a deal with the US and Britain to fund schools with a more balanced education.

Sheikh Umar said that while many northern Nigerians are as angry as Muslims elsewhere at events in the Middle East, they have not been radicalised by them: "You can't blame people who see injustice in Afghanistan and Iraq. But here we are more preoccupied with our local issues, fighting corruption and the like."

But extremism is sometimes not far from the surface. Earlier this month, a female teacher in Gombe spotted a student cheating during an exam on Islam and threw his books in the bin. The student, trying to cover up his wrongdoing, told other pupils that Oluwatoyin Oluseesin had desecrated the Qur'an. They beat her to death.

Backstory

About half of Nigeria's 130 million citizens are Muslim. They dominate the north,although there are sizeable Christian communities, which often leads to friction and, periodically, bloodshed. A Muslim presence dates back to the 12th century after north African scholars arrived on trade routes, bringing Islamic teachings and culture. Jihads followed from what is now Senegal. Britain used Islamic political and religious structures to administer the north. After independence a new political class and the military emerged. Thousands have been killed in recent years in religious violence, with Muslim attacks on northern Christian enclaves and Christians slaughtering Muslims in the south. The return to democracy in 1999 led to populist politicians getting elected on promises to widen Islamic law. Twelve states strengthened the sharia code, often banning alcohol, segregating the sexes in public, introducing amputations for theft, and stoning for adultery. Most severe punishments were not carried out.